Hypothyroidism refers to a condition which is defined by a low level of thyroid hormones. Hypothyroidism can lead to a wide range of symptoms being experienced which makes it a challenging condition to define based on clinical presentation (just on symptoms). For this reason, further testing is required to make a diagnosis of hypothyroidism.
Following blood tests, hypothyroidism can be described in a number of ways.
- Primary hypothyroidism is where the levels of TSH (thyroid stimulating hormone) are elevated. Alongside this, levels of free thyroxine (T4) are below the reference range.
- Mild or subclinical hypothyroidism is regarded as an early sign of thyroid dysfunction. This is seen where TSH levels are elevated but T4 levels are at normal levels. This indicated the thyroid is in the earlier stages of underperforming. In the case of subclinical hypothyroidism monitoring of blood tests is suggested. [Source: Pubmed]
The standard medical treatment for hypothyroidism is levothyroxine. This is a synthetic form of T4 and is used as a thyroid replacement hormone to bring blood levels back to acceptable levels. However, it is common for hypothyroid symptoms to persist in many patients even when blood levels have reached their normal levels.
What are the symptoms of hypothyroidism?
The signs and symptoms of hypothyroidism can vary between patients, however, there are common symptoms of hypothyroidism.
The symptoms of hypothyroidism include:
- Fatigue
- Lethargy
- Poor tolerance to the cold
- Weight gain
- Constipation
- Dry skin [Source: Pubmed]
It is not possible to diagnose hypothyroidism based on symptoms alone. This can be especially hard in elderly patients who typically present with fewer symptoms.
It has been reported that an increase in the severity of symptoms in the previous 12 months may predict hypothyroidism. However, a study examining 34 hypothyroid-related symptoms concluded that they could not predict hypothyroidism based on symptoms.
It has also been reported that 15% of those with Hashimoto’s report only a single symptom. [Source: Pubmed]
Due to the importance of thyroid hormones in regulating energy production within the body, suboptimal or low levels of these hormones can impact nearly all major organs. The best studied are its impact on the cardiovascular system.
The organs impacted and the signs and symptoms are outlined in the following table:
| Presentation | Signs and implications | |
| General metabolism | Weight gain, cold intolerance, fatigue | Increase in body-mass index, low metabolic rate, myxoedema, hypothermia |
| Cardiovascular | Fatigue on exertion, shortness of breath | Dyslipidaemia, bradycardia, hypertension, endothelial dysfunction or increased intima-media thickness, diastolic dysfunction, pericardial effusion, hyperhomocysteinemia, electrocardiogram changes |
| Neurosensory | Hoarseness of voice, decreased taste, vision, or hearing | Neuropathy, cochlear dysfunction, decreased olfactory and gustatory sensitivity |
| Neurological and psychiatric | Impaired memory, paraesthesia, mood impairment | Impaired cognitive function, delayed relaxation of tendon reflexes, depression, dementia, ataxia, Carpal tunnel syndrome and other nerve entrapment syndromes, myxoedema coma |
| Gastrointestinal | Constipation | Reduced oesophageal motility, non-alcoholic fatty liver disease, ascites (very rare) |
| Endocrinological | Infertility and subfertility, menstrual disturbance, galactorrhoea | Goitre, glucose metabolism dysregulation, infertility, sexual dysfunction, increased prolactin, pituitary hyperplasia |
| Musculoskeletal | Muscle weakness, muscle cramps, arthralgia | Creatine phosphokinase elevation, Hoffman’s syndrome, osteoporotic fracture (most probably caused by overtreatment) |
| Haemostasis and haematological | Bleeding, fatigue | Mild anaemia, acquired von Willebrand disease, decreased protein C and S, increased red cell distribution width, increased mean platelet volume |
| Skin and hair | Dry skin, hair loss | Coarse skin, loss of lateral eyebrows, yellow palms of the hand, alopecia areata |
| Electrolytes and kidney function | Deterioration of kidney function | Decreased estimated glomerular filtration rate, hyponatraemia |
What is the main cause of hypothyroidism?
In primary hypothyroidism, the most common cause of thyroid underperformance in autoimmune thyroiditis is known as Hashimoto’s disease. This is seen where alongside alterations in the level of TSH and T4, anti-thyroid antibodies are also seen.
The 2 anti-thyroid antibodies tested for are thyroid peroxidase antibodies and anti-thyroglobulin antibodies.
Autoimmune conditions occur when the patient’s immune system is no longer able to tolerate self-tissues. This means that the immune system can start attacking and damaging parts of the body which leads to dysfunction. In this case, it can be thought of as the immune system seeing the thyroid gland as an invader it needs to attack.
Also Read: Hashimoto’s Thyroiditis Symptoms
There is not a single cause of Hashimoto’s disease but it involves both genetic and environmental factors. This can include nutrient status (vitamin D and selenium), long-term dietary patterns as well as viral infections. [Source: Pubmed, Pubmed, Pubmed]
Causes of primary hypothyroidism include:
- Chronic autoimmune thyroiditis (also known as Hashimoto’s thyroiditis)
- Iodine—severe iodine deficiency, mild and severe iodine excess
- Drugs—eg, amiodarone, lithium, tyrosine kinase inhibitors, interferon-alfa, thalidomide, monoclonal antibodies (eg, ipilimumab and nivolumab), antiepileptic drugs (eg, valproate), drugs for second-line treatment of multidrug-resistant tuberculosis
- Iatrogenic—radioiodine treatment (eg, for Graves’ disease or toxic nodular disease), hemithyroidectomy, radiotherapy or surgery in the neck or head region
- Transient thyroiditis—viral (De Quervain’s syndrome), post-partum, silent thyroiditis, destructive thyroiditis
- Thyroid gland infiltration —infectious (eg, mycoplasma), malignant (eg, thyroid malignancy, lymphoma, metastasis of malignancy elsewhere), autoimmune (eg, sarcoidosis), inflammatory (eg, Riedels’s thyroiditis)
- Genetic —autoimmunity-related genes (eg, HLA class I region, PTPN22, SH2B3, and VAV3), general and thyroid-specific genes (eg, FOXE1, ATXN2, and PDE8B)
- [Source: Pubmed]
What is central hypothyroidism?
Central hypothyroidism is a rarer form of hypothyroidism and impacts males and females in equal amounts.
This is not seen as an issue with the thyroid gland itself, but with the parts of the body that regulate the functioning of the thyroid gland. These are the pituitary gland and the hypothalamus. [Source: Pubmed]
In central hypothyroidism, blood tests show a low or a low-normal result for the levels of thyroid stimulating hormone (TSH) and a reduced concentration of T4. In over 50% of the cases of this type of hypothyroidism, the caused is pituitary adenoma (a tumour that is not cancer).
Other causes of central hypothyroidism include hypothalamic dysfunction due to the factors listed below.
Causes of central hypothyroidism include:
- Pituitary tumours (secreting or non-secreting)
- Pituitary dysfunction (eg, Sheehan’s syndrome)
- Hypothalamic dysfunction (eg, post-traumatic)
- Resistance to thyroid-stimulating hormone (TSH) or thyrotropin-releasing hormone
- Drugs (eg, dopamine, somatostatins, glucocorticosteroids, and retinoid X receptor selective ligands)
- Increased TSH concentration due to leptin stimulation
- [Source: Pubmed]
Is iodine important for thyroid health?
Iodine is a trace mineral that is essential for thyroid hormone production. It has been shown that a deficiency can lead to goitre, thyroid nodules as well as hypothyroidism. [Source: Pubmed]
Levels of iodine have been monitored and their relationship to thyroid health studied. In certain populations, if iodine intake increases from a severe iodine deficiency to a mild iodine deficiency the rate of hypothyroidism decreases.
However, it has been found that in populations where there is an increase in iodine levels from a mild deficiency to optimal or excessive levels of iodine the rates of autoimmune thyroid disease actually increases. [Source: Pubmed, Pubmed]
It has also been found that certain medications that contain iodine can impact thyroid function through iodine overload. One study found that 14% of patients taking the heart medication amiodarone developed hypothyroidism. Another medication, lithium was also found to increase the likelihood of developing hypothyroidism. [Source: Pubmed Pubmed]. One study found that 6% of patients required thyroid replacement therapy within 18 months of starting lithium treatment. [Source: Pubmed]
What does hypothyroidism do to a person?
Thyroid hormones control and regulate metabolic processes within the human body. This means that the energy we ingest through the food that we eat is converted into a form of energy that can be used throughout the body. The thyroid is central to this process.
If the function of the thyroid gland is impacted this can lead to alterations in metabolic processes throughout the entire body, impacting most major organs. This can lead to dysfunction in areas such as:
- The gut – leading to constipation
- The cardiovascular system – leading to poor blood flow and fatigue
- Slowing repair processes – leading to dry skin and brittle hair [Source: Pubmed]
Since the role of thyroid hormones is central to energy production and balance within the body, one way to understand symptoms of hypothyroidism is when biological processes start to slow down. This slowing can result in slow bowel movements, low mood and low levels of energy. [Source: Pubmed]
Hypothyroidism diet
Certain nutrients are required for thyroid health these can be found in certain foods to support thyroid function.
The nutrients and their sources are:
- Iron – liver, red meat, beans (such as red kidney beans, edamame beans and chickpeas), nuts, dried fruit – such as dried apricots.
- Iodine – Seaweed (nori, kelp, kombu, wakame), fish, shellfish (cod, canned tuna, oysters, shrimp), dairy (milk, cheese, yoghurt), eggs, beef liver, chicken.
- Copper – liver, oysters, spirulina, nuts and seeds, lobster, leafy greens.
- Selenium – pork, beef, turkey, chicken, fish, shellfish, eggs, Brazil nuts.
- Zinc – oysters, red meat, poultry, beans, nuts, crab and lobster.
It may also be beneficial for some of these nutrients to be taken in the form of supplements.
Working with a registered practitioner can help guide the appropriate doses of these.
Hypothyroidism tests
Blood tests are required for a diagnosis of hypothyroidism. The 2 most tests that are routinely carried out are for TSH and T4.
- TSH – thyroid stimulating hormone
- T4 – total thyroxine
To assess for thyroid autoimmunity thyroid antibodies can also be measured. This can help to identify the underlying causes of the underactive thyroid and help guide the approach.
The thyroid antibodies are:
- thyroid peroxidase antibodies
- anti-thyroglobulin antibodies.
Hashimoto’s disease (autoimmune thyroiditis) is the most common cause of hypothyroidism there assessing for thyroid antibodies can be an important aspect of the diagnostic process. [Source: Pubmed]
How can I improve my gut health with hypothyroidism?
Due to the connection between the gut and the thyroid, supporting and improving the health of both of these areas can be the best approach.
From a gut perspective, there are key areas that can be supported to improve gut health.
One of the key areas for supporting the gut and the gut microbiome is the type of food that is consumed. The template that can provide the most diverse intake of plant foods, as well as the most amount of fermentable fibre, is the Mediterranean diet.
This dietary template includes key points such as:
| Ingredient | Frequency of consumption |
| Variety of unprocessed or minimally processed whole grains, cereals, and legumes | Regular staple |
| Variety of fresh fruits, vegetables, and salads | Daily basis (seasonal varieties) |
| Dry fruits, nuts, seeds, honey | Regular basis (generally as snacks) |
| Extra-virgin olive oil; fish oil | Principal source of fat (rich in poly- and mono-saturated fatty acids; low in saturated fat) |
| Poultry (eggs and chicken) | Low to moderate consumption |
| Sea food (fish, oysters, sea weeds) | Low to moderate consumption |
| Red and processed meats | Very low consumption |
| Unprocessed or minimally processed cheese and yogurt | Low to moderate consumption |
| Wine | Low to moderate (occasionally; particularly with evening meals) |
The gut health benefits of this type of intake of food have been researched in-depth and have been found to improve gut health in several ways. This includes:
- Improving the balance of the beneficial bacteria
- Supporting the production of short-chain fatty acids, the main energy source for the gut lining
- Supporting the immune system in the gut
- Reducing gut inflammation
- Reducing gut permeability
- Reducing depression and stress
- Reducing systemic inflammation
- Improving cholesterol levels [Source: Pubmed]
Do probiotics help hypothyroidism?
Probiotics are described as non-pathogenic microorganisms that have a beneficial effect on the host. In hypothyroidism, low levels of key gut bacteria have been reported.
Studies have indicated that probiotics administration can help to improve many aspects of thyroid health. These include helping to balance levels of T4 and T3 and reducing levels of TSH.
Some of these studies have been carried out in animals, however, human studies using probiotics have resulted in a reduction in TSH levels as well as thyroid patients being able to reduce the dose of their thyroid medication. This indicated the beneficial impact on thyroid health simply by supporting the gut. [Source: Pubmed]
Probiotics can positively impact levels of selenium, zinc and copper, all required for thyroid health. It has also been found that gut microbes act as a store of T3 (the active form of thyroid hormone).
This is another reason why a healthy gut can support the levels of thyroid hormones and potentially reduce the need for T4 medication. [Source: Pubmed]
Also Read: How To Lose Weight With Hypothyroidism
Does hypothyroidism cause IBS?
Thyroid hormones support muscle function and contractions within the gut. This means that poor thyroid health can lead to reduced motility of the gut. The reduced motility can then contribute to symptoms, such as dyspepsia, constipation and IBS.
The symptoms of dyspepsia include:
- Pain or a burning sensation in the stomach after meals
- Bloating or belching after meals
- Feeling full very quickly
- Pain or discomfort in the stomach [Source: MayoClinic]
The muscle contractions within the small intestine help in regulating the microbial balance. However, if these muscle contractions are altered, this may then lead to changes in the microbial balance in the small intestine. This is a reason why an underperforming thyroid gland is considered a risk factor for SIBO due to the slow movement of the muscles in the small intestine creating an environment that allows more bacteria to flourish.
SIBO stands for small intestinal bacterial overgrowth and is defined by an increase in the bacterial load within the small intestine. SIBO has been indicated to be the underlying cause of symptoms in up to 80% of those with IBS [Source: Pubmed]. This condition has also been reported to be present in up to 50% of those with an underactive thyroid [Source: Pubmed]
Even without digestive symptoms such as bloating, constipation and dyspepsia, imbalances in the gut bacteria can still be present. These imbalances may then further impact the functioning of the thyroid gland.
Can gut health affect your thyroid?
Gut health and thyroid health are closely linked. The communication pathways between these 2 parts of the body are called the thyroid-gut axis. This refers to the communication pathways and how these 2 areas of the body support each other. It is also possible for changes in this pathway to contribute to dysfunction.
For example, changes within the gut can include factors such as:
- Imbalances in bacteria
- Increased inflammation
- Reduce immune tolerance
- Damage to the gut lining
- Increased intestinal permeability (leaky gut)
Due to the role of the gut and its influence on supporting the absorption of nutrients that are required for thyroid function, reduced uptake of these nutrients can have a detrimental effect on thyroid hormone production. These nutrients include iodine, selenium, zinc and iron and low levels of these has is associated with poor thyroid function. [Source: Pubmed].
Imbalances in the gut have been linked to autoimmune processes via several possible mechanisms, all of which influence the immune response and progression.
These include:
- Molecular mimicry
- Bystander activation
- Epitope spreading [Source: Pubmed]
Additionally, changes in the lining of the gut have been seen in those with Hashimoto’s thyroiditis, in particular in the duodenum (the first part of the small intestine). These changes included a thickening in the microvilli as well as an increased space between these which may indicate alterations in the structure of the gut wall that may contribute to the local and systemic immune response which can contribute to an autoimmune response [Source: Pubmed].
Conclusion
Due to the interaction between the thyroid and the gut, supporting both aspects can be key when addressing an issue in either.
Working with a registered Nutritional Therapist can help guide this approach and take the guesswork out of getting your health back on track.
